WLCSP refers to the technology of packaging an integrated circuit at wafer level, instead of the traditional process of assembling the package of each individual unit after wafer dicing. Conventional WLCSP technology extends wafer fab processes to include device interconnection and device protection processes.
A conventional method to implement WLCSP technology for small die requires that the die on a primary wafer be scribed and separated from the wafer. The die are then placed further apart on a secondary wafer so solder balls used to connect the die to a printed circuit board (PCB) will have enough space without affecting the next die. When the die are cut from the primary wafer and placed in the secondary wafer, the die need to be aligned perfectly or the results will be compromised. A separate process distributes the original bond pads to the now spaced-out ball pads. The use of the secondary wafer and the corresponding additional process steps results in a time-consuming and expensive WLCSP solution.
Another conventional method to implement WLCSP is to re-layout the die to a bigger size to accommodate the bigger pitch of the target balls. This method is also time-consuming and expensive because another die must be created with a different layout, which requires additional design time. Additionally, product and quality control personnel need to characterize and test the new design to ensure it operates within the design specifications. Customers may need to re-qualify the new die if they were using the original die.